Respiratory Sinus Arrhythmia in Apnea Patients With Apnea Associated Comorbidities

The strength of the Respiratory Sinus Arrhythmia (RSA) in patients with Obstructive Sleep Apnea (OSA) might help to understand the correlation between apnea and Cardiovascular Diseases (CVD). For estimating the RSA, Heart Rate Variability (HRV) analyses can be used. The High Frequency (HF, 0.15 Hz–0.4 Hz) band of the power spectrum of the tachogram is recognized to contain the information related to breathing. However, this assumption might produce wrong RSA estimates, since the respiratory rate can occur outside the HF band. In this work, the strength of the RSA in OSA patients with apnea associated comorbidities was estimated using respiratory and electrocardiogram (ECG) signals. For this, the shared frequency content between respiration and HRV was characterized with methods that calculate respiratory frequency bands different to the HF. These methods were applied in a dataset of OSA patients and apnea-associated comorbidities. Even though there were no significant differences between groups, patients with more severe apnea and comorbidities presented an apparently higher RSA level. This observation might illustrate the function of the RSA as a compensation mechanism to reduce the workload exerted by the heart and to compensate for an abnormal blood pressure.